11-05-09 FC Stormwater Standards and Guidelines · 2018-11-28 · Angela Milewski - BHA Design Inc. Jason Messaros - BHA Design Inc. Glen Schlueter - City of Fort Collins Uti liti

City of Fort CollinsLandscape Design Standards and Guidelines

forStormwater and Detention Facilities

November 5, 2009

PREPARED BY BHA DESIGN INC. WITH CITY OF FORT COLLINS UTILITY SERVICES

ACKNOWLEDGEMENTS 2

ACKNOWLEDGEMENTS:

STEERING COMMITTEE AND CONTRIBUTORS

Rodney Albers - City of Fort Collins Uti liti esJusti n Morrison - Mountain-n-Plains Real Estate Services

Michael Bello - Larkspur Homes, LLCLes Kaplan

Stu MacMillan - Everitt -MacMillanJim Sell - Jim Sell Design, Inc.

Jason Claeys - Jim Sell Design, Inc.Matt Blakely - Jim Sell Design, Inc.Jennifer Williams Almstead - VFRNick Haws - Northern Engineering

Herman Feissner - Feissner Consulti ng, LLCBrad Anderson - Anderson Consulti ng Engineers, Inc.

Steve Long - Cedar Creek Associates, Inc.Basil Hamdan - City of Fort Collins Uti liti esDana Leavitt - City of Fort Collins Planning

Steve Olt - City of Fort Collins Current PlanningMark Sears - City of Fort Collins Nat Resources

Angela Milewski - BHA Design Inc.Jason Messaros - BHA Design Inc.

Glen Schlueter - City of Fort Collins Uti liti esLisa Kokes - City of Fort Collins Uti liti esLouise Herbert - Landscape Architect

TABLE OF CONTENTS 3

City of Fort CollinsStormwater Standards and Guidelines

TABLE OF CONTENTSINTRODUCTION 1

VISION AND GOALS 1STRUCTURE 1VARIANCE PROCEDURES 1

BACKGROUND 2CONCEPTS 2INFILTRATION VS. RUNOFF 2HABITAT VALUE 2STORMWATER IS AN AMENITY 3

OBJECTIVES 4DESIGN GUIDELINES 5

GENERAL CONSIDERATIONS 5PLANNING/SITE CONTEXT 5LANDFORM AND SLOPES 6PLANTING DESIGN 8PLANT SPECIES SELECTION 8TABLE 1: RECOMMENDED PLANT LIST 9PLANTING TECHNIQUES 10IRRIGATION 12MAINTENANCE 13

APPENDICES 14GLOSSARY OF TERMS & CONCEPTS 14

STAKEHOLDER & OPEN HOUSE COMMENTS 16

4

CIPO: Multi-Use Basin - Detention, Water Quality, Passive Recreation, Habitat Restoration

CIPO: Integrated Outfall Structure CIPO - Habitat, Bio-Mimicry

INTRODUCTION 1


INTRODUCTION

The following standards and guidelines have been developed to inform the design and maintenance of landscaping within storm drainage and detenti on faciliti es in Fort Collins. Currently the City of Fort Collins follows writt en standards for the technical design of drainage and detenti on faciliti es. These faciliti es represent a signifi cant porti on of open space within both public and private developments in the city. As a result, these standards and guidelines will improve the overall character of our community, storm drainage functi on, reduce irrigati on demand, improve wildlife habitat, and promote maintenance of these open areas.

VISION AND GOALSThese standards and guidelines are part of a

larger vision of both the City of Fort Collins City-Wide Sustainability Initi ati ve and the 21st Century Uti liti es Initi ati ve. This vision is:

“To inspire community leadership by reducing environmental impacts while benefi ti ng customers, the economy and society”

In order to help achieve this vision, these standards and guidelines for landscaping have been developed with the following goals:

Promote water infi ltrati on and water quality ●Habitat value and plant conservati on ●Improve aestheti c quality ●

STRUCTUREThis document includes background informati on

and describes concepts and objecti ves for design of stormwater faciliti es to meet the goals of the 21st Century Uti liti es Initi ati ve. It includes both guidelines (suggested recommendati ons for design improvements) and standards (mandatory requirements for design or documentati on). The standards or requirements are outlined a the end of each secti on.

This document is intended to supplement, not supercede, current regulatory documents which may include:

Fort Collins Land Use Code ●Fort Collins Stormwater Design Criteria Manual ●

Larimer County Urban Area Street Standards ●Army Corps of Engineers ●Neighborhood Home Owner’s Associati on ●RequirementsNeighborhood Design Review Committ ee ●Requirements

VARIANCE PROCEDURES These standards and guidelines illustrate and regulate

the implementati on of the concepts and objecti ves of the 21st Century Uti liti es Initi ati ve. Their purpose is to convey these fundamental concepts, but also to foster design innovati on and collaborati on between city staff , developers, and design professionals. Proposed designs that illustrate the spirit and accomplish the goals, but do not conform to these standards must be approved by the City of Fort Collins Uti liti es Executi ve Director or the Director’s designee. A variance request shall be submitt ed in writi ng prior to or as part of an applicati on for development review. The variance request (s) shall include:

Identi fying Issue ● : Identi fi cati on of the standard to be waived or varied and why the standard is unfeasible.Alternate Design ● : Identi fi cati on of the proposed alternati ve design or constructi on criteria.Comparison to Standards ● : A thorough descripti on of the variance request and how the new design compares to the standard. Justi fi cati on ● : Indicati on of how the proposed plan (as varied) advances the purpose of the standard sought to be varied equally well or bett er than would compliance with such standard.

Based upon review of the plans and additi onal informati on submitt ed, the Director may approve or deny the variance request. If the Director of Uti liti es approves the variance request, the plans will conti nue to be reviewed and approved within the typical review process. If the Director denies the variance request, the applicant shall subsequently submit revised plans in compliance with these Standards. The Director shall provide a writt en response outlining the basis for all approvals or denials of variance requests.

BACKGROUND 2

BACKGROUND

CONCEPTSThe basic concepts of stormwater management are

not complicated. The goal is to restore the hydrological cycle to the extent possible and to uti lize the available precipitati on to promote a naturalized environment in developed areas. This requires understanding the pre-development conditi ons so they can be an integrated system in the development.

Site stormwater design should not simply focus on basin sizing and outf all rates, but should address site drainage as an integrated multi -use hydrologic system. This system may include detenti on, water quality treatments, stream bank erosion control, habitat creati on, infi ltrati on, energy dissipati on, and/or recreati onal use. The concepts here illustrate specifi c measures which aff ect landscape treatments within this overall, integrated stormwater design approach.

INFILTRATION VS. RUNOFFInfi ltrati on is a natural process by which precipitati on is

absorbed into the soil. Depending on the local soil type, some of the water remains in the top layers of soil and is used by vegetati on. The rest of the water percolates

through the soil and bedrock, recharging the groundwater system.

Runoff occurs when the soil is saturated, has become impermeable or when structures and impermeable materials are placed on the site. Runoff tends to contain silt and pollutants that require miti gati on. Excessive runoff also contributes to adverse hydraulic downstream conditi ons causing unnatural stream bank erosion and limited groundwater recharge.

Appropriate site design promotes natural infi ltrati on resulti ng in fewer downstream impacts including excessive steam fl ow, exaggerated geomorphology, and reduced stormwater capacity of natural systems.

HABITAT VALUEHistorically the area that is now Fort Collins was a

short grass prairie with a large variety of plant and animal species. Many of these species have been displaced by the onset of development. Natural waterways and drainage patt erns are altered by development. This decreases the functi onality of existi ng hydrologic systems. It is necessary to reasonably accommodate and/or reestablish the hydrologic systems that existed prior to development through the site and landscape design process.

Naturalized Planting - Improved Habitat Value

PRE-DEVELOPMENT POST-DEVELOPMENT(TYPICAL)

GOAL: POST -DEVELOPMENTDESIGNED FOR INFILTRATION

RUNOFF

INFILTRATION

INCREASEDRUNOFF

DECREASEDINFILTRATION

DECREASERUNOFF

INCREASEINFILTRATION

BACKGROUND 3


STORMWATER IS AN AMENITYStormwater faciliti es have a reputati on for being

functi onal site features without natural qualiti es. The basic design parameters for a detenti on pond design is capacity or volume and rate of discharge. These parameters combined with economic factors typically result in designs that maximize the amount of stormwater detenti on within the smallest possible area.

These parameters are typically accomplished by the creati on of geometric basins with calculated volume and outf low rates, connected to site and local uti liti es through standard gray concrete and steel structures. The typical detenti on basin is functi onal as a facility, yet, provides litt le or no aestheti c or habitat benefi ts. In many cases detenti on basins of this kind detract from the overall project image or appeal and adversely aff ect surrounding properti es.

Detenti on ponds and waterways can instead be designed to both meet the engineering requirements and provide an att racti ve diverse space. A detenti on pond can serve as a multi -use area, wildlife habitat, picturesque scene, entry experience or educati onal opportunity while maintaining the necessary functi ons of stormwater detenti on and water quality improvement. Stormwater faciliti es should be considered an opportunity for aestheti c interest and natural integrati on rather than solely necessary features of a development.

“Front Door” Curb Appeal - Improved Aesthetics

OBJECTIVES 4

OBJECTIVESIn order to achieve the overall goals, the following

objecti ves must be met:

INFILTRATION AND WATER QUALITY1. Reduce excess runoff and downstream polluti on by

increasing on-site infi ltrati on and water quality. Maintain the primary functi ons of detenti on ponds and stream drainages to att enuate fl ows and improve water quality while creati ng and improving wildlife habitat.

Increase pervious surface area and surface ●conveyance.Decrease fl ow concentrati on. ●Take advantage of natural processes through ●bio-fi ltrati on and bio-retenti on.Manage vegetati on to insure proper drainage ●functi ons are maintained while allowing habitat values to be expressed to the extent possible.

HABITAT VALUE AND PLANT 2. CONSERVATION

Create and protect habitat for a diverse array of plants and animals; birds, mammals, insects, amphibians, and wetland plants.

Increase plant species diversity including the number ●and variety of butt erfl y host plant grasses, forbs, and shrubs as well as the number of nectar plants and shelter plants.Increase the number and variety of nati ve shrubs and ●trees that provide valuable cover, berries, insects, nest sites and other resources for migratory, nesti ng, and wintering birds.Increase the number and variety of wetland species ●that provide opti mal conditi ons for amphibian and repti le breeding to occur.

AESTHETIC APPEAL3. Create a beauti ful landscape that people will enjoy

and appreciate without sacrifi cing functi on and value for wildlife and plant habitat.

Increase the amount of shade and resti ng areas along ●trails and open spaces while providing habitat for wildlife and viewing opportuniti es for visitors.Use plant species that maintain their beauty in a ●variety of seasons, such as a species with colorful

and showy fl owers, fall leaf color, winter texture, and grasses that persist through the winter while they provide good wildlife habitat.Use vegetati on to frame viewsheds and enhance the ●natural aestheti c qualiti es of the site.

DESIGN GUIDELINES 5


DESIGN GUIDELINES

GENERAL CONSIDERATIONSA signifi cant porti on of a developed site oft en must

be used for drainage conveyance and site detenti on. In planning your site, consider how the storm drainage faciliti es can contribute to the overall character of the project.

Developers and designers should consider:How will the stormwater faciliti es be designed to ●achieve the goals of this document and the needs of the project?How will the stormwater faciliti es be designed as an ●amenity rather than a necessary nuisance for this project?

PLANNING/SITE CONTEXTObtain and understand informati on about site

conditi ons and site context before designing the detenti on faciliti es, including:

Adjacent and regional drainage, recreati onal, and ●open space patt ernsOn-site topography and drainage conditi ons ●Soil conditi ons ●Unique natural features, ameniti es or views ●Aestheti c expectati ons ●

Consider how the design of drainage faciliti es and detenti on areas can contribute to the overall plan and adjacent developments. Collaborate with adjacent property developers to formulate a more eff ecti ve neighborhood or regional storm drainage plan. Look for opportuniti es to integrate storm drainage conveyance and water quality systems into the planned development. Using bioswales, linear conveyance with check dams, and inverted landscape islands throughout the project will increase distributed infi ltrati on and can result in reduced land dedicati on requirements for larger detenti on ponds.

Diff erent development types will have diff ering needs that can be enhanced by thoughtf ul design of stormwater systems that can serve multi ple functi ons. Some concepts to consider for detenti on areas based on development types include:

Residenti al Development ● – neighborhood greenbelts, multi -purpose recreati onal fi elds*, pedestrian trails, entry features, water features, wildlife habitat, wetland/riparian ameniti es, community gardens*, orchards, natural playgrounds, off -leash dog play areas*.

Business / Retail Development ● – Water features, entry features, loop trails, picnic shelters*, visual buff er to screen service areas from public spaces, bioswale/landscape islands, etc.

Industrial Development ● – Visual buff er to screen service and loading areas, trail connecti ons, recreati on areas, etc.

* Structures and fences should be designed for fl ooding conditi ons.

DESIGN GUIDELINES 6

LANDFORM AND SLOPESDetenti on ponds engineered solely to meet the

minimum holding capacity of the required storm fl ows generally result in ponds with uniform side slopes with litt le natural character, or with verti cal side walls that may create unsafe conditi ons. Design pond slopes in a way that they may also contribute to other goals.

If a detenti on pond is designed to also serve as a neighborhood recreati on or athleti c fi eld, use gentle side slopes to allow for easy access to the play fi elds. Steeper side slopes can be designed with terraced fl at areas to serve as spectator seati ng. Other greenbelt ameniti es such as picnic areas and pedestrian trails can be developed adjacent to these spaces to create a neighborhood park amenity that also serves as stormwater detenti on. While gentler slopes for detenti on may require more land for the pond, by combining the required pond area with required community uses, less land may be used for these open areas overall.

Multi-Use Basin: Detention & Passive Recreation, Trails

Multi-Use Basin: Detention & Passive Recreation

Multi-Use Basin: Detention & Sports Field

Multi-Use Basin: Detention & Passive Recreation, Trails

THIS NOT THIS

DESIGN GUIDELINES 7


Detenti on ponds designed to be naturalized open space should include varied side slopes and an undulati ng bott om. Varied slope conditi ons will promote opportuniti es for plant diversity and wildlife habitat by creati ng subtle changes in elevati on above the average water level. Combine these techniques to create a wide array of diverse soil conditi ons and exposures for plants and animals to inhabit and “naturalize”.

Design detenti on ponds with positi ve slopes (2% minimum) near the outlet to avoid standing water and limit mosquito habitat. Manicured turf areas that require regular mowing should also be sloped to drain appropriately (4:1 Max). However, fl att er areas are encouraged to increase infi ltrati on, but must be landscaped appropriately with wetland plants, forbs and shrubs that do not require regular mowing and will tolerate wet and dry conditi ons.

Avoid the use of concrete trickle pans in areas with well-draining soils as they reduce infi ltrati on and promote evaporati on and increased runoff . Where necessary, trickle pans shall be designed as an integrated part of the landscape. Horizontal alignment shall complement topographic character and be non linear. Embedded cobbles and/or boulders are encouraged. Color shall be a subtle earth tone.

General access is a primary safety considerati on. Ramped access and gentle side slopes allow people and animals to evacuate the basin in the event of high water.

Access for maintenance equipment and personnel is necessary for proper care and management of stormwater faciliti es. Design slopes to provide appropriate access for wheeled service vehicles, uti lity vehicles, lawn mowers

and/or brush hogs. Consider that trash and debris must be regularly removed by maintenance personnel. Periodic cleanup operati ons may also require the use of heavy equipment. If walls are used, they shall be limited to the minimum required height and length needed. Ideally no more than 50% of a basin perimeter should be bound by walls. All walls shall be built of suitable materials matching adjacent architecture or designed into the landscape scheme with natural stone or integral color concrete with form liner.

LANDFORM AND SLOPESRequired Design Standards:

In all cases the following standards apply:No concrete trickle channels shall be used where ●free draining soils are present (Soil Group A, B). Limit their use to areas with clayey soils (Soil Group C, D) if necessary.Side slopes should vary and range from 4:1 to 20:1 ●No vegetated slope should exceed 3:1 ●Landscaped areas should slope to drain (2% ●minimum) or be planted appropriately so regular mowing is not required (see PLANTING DESIGN secti on).Basin area cannot be 100% bound by walls. All ●walls proposed for the pond perimeter are required to have a high quality visual character (such as natural stone or integral color concrete with form liner). Walls should not exceed 30” in height. Fences may be required for safety.Provide a minimum of one entry point for regular ●access by maintenance vehicles and mowers, and for occasional access by heavy equipment if necessary. Provide adequate egress to allow users to safely evacuate the area in the event of high water.

THIS NOT THISNaturalized drainage channel slows drainage, promotes infi ltrati on, allows for habitat

establishment

Concrete trickle channel eliminates infi ltrati on and promotes

evaporati on and excessive runoff

DESIGN GUIDELINES 8

PLANTING DESIGNThere is no universal approach to landscape design for

detenti on areas. Planti ng design must respond to site-specifi c stormwater functi ons, soil types and hydrology, slopes, solar aspect, availability and type of irrigati on, habitat creati on, planned uses and planned maintenance. A Landscape Architect can assist with a comprehensive plan for the landscape design for your project’s open space and detenti on areas. The following guidelines outline important criteria for the development of landscape plans for these areas.

Before fi nalizing planti ng plans and seed mixes, obtain horti cultural testi ng of the on-site soils where planti ng will occur. Testi ng can be completed by the Colorado State University Soil and Crop Sciences Department for a nominal fee. Contact the Soil-Water-Plant Testi ng Lab at htt p://www.extsoilcrop.colostate.edu/SoilLab/soillab.html for more informati on. Oft en planti ng plans must be completed before constructi on acti viti es take place, so fi nal soil conditi ons for areas to be planted are not available at the ti me of design. If overlot grading is planned to occur aft er the planti ng plans are complete, require the contractor to incorporate 6” of topsoil from on-site or imported source into fi nal grading operati ons, and indicate that the fi nal seed mixes will be modifi ed aft er fi nal grading is complete and subsequent horti cultural tests are evaluated.

Use nati ve and adapted plants. Proper landscape design with nati ve plants based on a site’s unique conditi ons can:

Reduce or eliminate need for supplemental irrigati on ●Reduce ferti lizer and chemical pest control needs ●Enhance wildlife habitat ●Reduce maintenance needs ●

Plants should be screened for invasiveness by using the Nature Conservancy’s Nature Serve Explorer website at htt p://www.natureserve.org/explorer/servlet/NatureServe?init=Species

PLANT SPECIES SELECTIONDelineate planti ng zones with similar characteristi cs

and proposed functi on. Characteristi cs should include slope, aspect, soil type, and moisture levels. Functi ons may include wildlife habitat, recreati onal use, or visual amenity or visual screening.

Develop a plant list for each zone type. See TABLE 1 for a sample listi ng of appropriate plant types.

DESIGN GUIDELINES 9


TABLE 1: RECOMMENDED PLANT LIST

TREES AND SHRUBS

Upland Species – North and East FacingFourwing Saltbush (Atriplex canescens)Rubber Rabbitbrush (Chrysothamnus nauseosus)Three-leaf Sumac (Rhus trilobata)Nati ve Smooth Sumac (Rhus glabra)Wood’s Rose (Rosa woodsii)White Snowberry (Symphoricarpos alba)Western Snowberry (Symphoricarpos occidentalis)Netleaf Hackberry (Celti s reti culate)

Upland Species – South and West FacingFourwing Saltbush (Atriplex canescens)Rubber Rabbitbrush (Chrysothamnus nauseosus)Three-leaf Sumac (Rhus trilobata)Desert False Indigo (Amorpha canescens)Winterfat (Krascheninnikovia lanata)Yucca (Yucca glauca)

Species for Moist, Well-drained Areas (2.5-6 feet above high water line or one-year storm)Saskatoon Serviceberry (Amelanchier alnifolia)Shiny-leaved Hawthorn (Crataegus erythropoda)Wild Plum (Prunus Americana)Western Chokecherry (Padus virginiana var. melanocarpa)Western Sand Cherry (Prunus bessyi)Cott onwood Tree (Populus spp.)Netleaf Hackberry (Celti s reti culate)

Species for Subirrigated Areas (1-3 feet above high water line)Leadplant (Amorpha fruti cosa)Redosier Dogwood (Cornus sericea)Golden Currant (Ribes aureum)American Black Currant (Ribes americanum)Peachleaf Willow (Salix amygdaloides)

GRASSES

Species for Upland SlopesLitt le Bluestem (Schizachyrium scoparium)Side Oats Grama (Bouteloua curti pendula)Blue Grama (Bouteloua gracilis)Western Wheatgrass (Pascopyrum smithii)Green Needlegrass (Nassella viridula)Slender Wheatgrass (Elymus trachycaulus)Buff alograss (Buchloe dactyloides)Bott lebrush Squirreltail (Elymus elymoides)Sand Dropseed (Sporobolus cryptandrus)Alkali Bluegrass (Poa juncifolia)Sun Sedge (Carex inops ssp. heliophila)

Species for Subirrigated AreasBig Bluestem (Andropogon gerardii)Switchgrass (Panicum virgatum)Yellow Indiangrass (Sorghastrum nutans)Alkali Sacaton (Sporobolus airoides)Green Needlegrass (Nassella viridula)Western Wheatgrass (Pascopyrum smithii)Nutt all Alkaligrass (Puccinellia airoides)Canada Wildrye (Elymus canadensis)

Species for Wetland AreasPrairie Cordgrass (Sparti na pecti nata)Canada Wildrye (Elymus canadensis)Switchgrass (Panicum virgatum)Inland Saltgrass (Disti chlis spicata)Fowl Bluegrass (Poa palustris)Nebraska Sedge (Carex nebrascensis)Woolly Sedge (Carex lanuginose)Creeping Spikerush (Eleocharis palustris)Torrey’s Rush (Juncus torreyi)Balti c Rush (Juncus balti cus)

DESIGN GUIDELINES 10

PLANTING TECHNIQUES

Soil PreparationGood soil is the foundati on of a successful landscape.

Planti ng areas require topsoil with appropriate levels of organic matt er. Spread imported or stockpiled topsoil to a minimum depth of four inches over areas to be planted. For nati ve seed areas, additi onal soil amendments are not necessary. Nati ve plants are adapted to the nati ve soils, and the additi onal organic matt er found in soil amendments may instead promote weed growth.

Sub-grade in planti ng areas should be loosened to a minimum depth of twelve (12) inches overall (8” of existi ng sub-grade and 4” of new topsoil). Remove stones and clods that could impede planti ng, seeding, and mowing. Stones protruding from the soil more than 3” should be removed. Collect and legally dispose of sti cks, roots, rubbish, and other extraneous matt er. Repeat culti vati on in areas where equipment used for hauling and spreading topsoil has compacted the soil. Fine grade disturbed planti ng areas to a smooth, uniform surface plane with a loose, uniformly fi ne texture. Grade to within the acceptable tolerances provided by the certi fying civil engineer. Roll and rake, remove ridges, and fi ll depressions to meet fi nish grades based on grading plans.

Weeds thrive in soil disturbed by grading operati ons. Use of appropriate herbicides prior to planti ng can help to reduce the onset of noxious weeds and other aggressive non-desirable plants. Apply non-selecti ve herbicides to weeds aft er fi ne grading has occurred and prior to planti ng. Herbicide shall be ‘Round-Up’ or similar product that will not persist in the soil and negati vely aff ect planti ng operati ons.

Seed Mixes and Installation TechniquesSeed mixes should be developed based on the on-site

soil conditi ons determined with the soil horti cultural tests. Since detenti on and drainage areas have varying moisture conditi ons and slopes, develop a diverse seed mix with a wide ecological amplitude. When multi ple seed species are used, they will tolerate a wide array of soil and moisture conditi ons. See TABLE 1 for a list of appropriate grass types for various planti ng zones.

Drill seed specifi ed mix in two passes, each at right angles to each other. Drill half of the seed in each pass. If areas are too wet or steep to drill seed, broadcast seed in two opposite directi ons. Restore fi ne grade aft er seeding, and cover seed to depth of 1/4 inch by raking or dragging. Firm seeded areas with a roller weighing maximum of 100 lbs. per foot of width.

Use of erosion control blankets may be needed on steeper slopes (greater than 6:1), or non-irrigated south-facing and west-facing slopes to reduce erosion, improve soil moisture and seed germinati on. Natural fi ber blankets are preferred to syntheti c blankets which can entangle repti les and amphibians in pond setti ngs. Install erosion control blankets as per manufacturer’s recommendati ons.

Remaining seeded areas should be mulched to reduce seed loss and improve soil moisture and germinati on. Large sites without irrigati on can be mulched with straw mulch. Straw mulch should be certi fi ed weed-free hay or certi fi ed weed-free straw with no seed heads, crimped into the seed bed aft er seeding has occurred. Irrigated sites can be hydromulched aft er seeding has occurred.

Wetland Plantings and Subirrigated Plugs Concentrate wetland planti ngs in areas where erosion

is anti cipated or where favorable moisture zones are likely to exist. Since planned moisture levels are diffi cult to predict, plant species in, above, and below their ideal zone to accommodate for both high water and low water seasons. Plants are then likely to establish in their opti mal conditi ons. Since detenti on areas fl uctuate with storm conditi ons, use species with wider tolerances to moisture conditi ons.

Wetland plugs may be necessary in areas that cannot be seeded due to constant inundati on or saturati on. Plant plugs aft er drill seeding from mid-May through July. Planti ng small plugs in the fall is less desirable due to loss of plants to Canada Geese. Plug planti ngs can be completed immediately aft er seeding. Subsequent plug planti ngs are recommended aft er initi al seed establishment when weeds are under control (2-5 seasons aft er initi al constructi on). These later planti ngs can be concentrated in bare areas and those areas needing erosion control protecti on.



Wetland plugs may be planted 12” to 24” on center and may need protecti on with turf reinforcement mats, jute or similar erosion control devices. Plugs can be caged or covered with wire fabric, jute or other products for protecti on if damage by geese or small mammals is anti cipated. In areas of standing water, grids of string slightly above the water elevati on can also be installed to reduce waterfowl access to newly planted areas.

Trees and ShrubsConcentrate or group shrubs and woody plants into

beds or groups to more quickly create habitat for wildlife and to reduce weeding, watering and maintenance requirements. Select species based on the opti mal moisture zones. Construct planti ng wells around each tree or group of woody plants to capture natural moisture for the plants. Use organic mulch in planti ng beds or in tree wells to increase moisture retenti on and to reduce weed and grass encroachment. Avoid using weed barrier around trees an shrubs.

Use shrubs and wetland plants strategically near inlets to soft en the visual impact of these man-made structures without impeding storm drainage functi on. Avoid the use of exposed rip-rap. Rip-rap if used shall be a subtle earth tone color, not pink, and should be buried and integrated with erosion control matti ng, and planti ng to soft en the visual impact and provide opportuniti es for habitat establishment. Other types of less intrusive erosion control materials which incorporate planti ng materials should be considered. Bio-engineered soluti ons are preferred in lieu of structural erosion control measures. Brush layering and use of live branch cutti ngs can restore and protect stream banks and outf all areas while creati ng

a natural habitat and reduce the cost of structured protecti on measures. Seeding schedule should be per seed source recommendati on. Trees and shrubs should be planted prior to seeding.

LANDSCAPERequired Design Standards:In all cases the following standards apply:

Enlist the services of a Landscape Architect to ●prepare the required landscape constructi on plans for commercial project detenti on areas.Develop plant lists and seed mixes based on ●horti cultural testi ng of site soil conditi ons.Delineate planti ng zones based on soil ●characteristi cs and functi on. Develop plant lists appropriate for each planti ng zone.Use nati ve and adapted plants. ●Provide a minimum of one entry point for regular ●access by maintenance vehicles and mowers, and for occasional access by heavy equipment if necessary. Do not block access with designed landscape features.Stockpile and redistribute (or import if necessary) a ●minimum of four inches of topsoil over areas to be planted. Use non-persistent herbicide prior to planti ng to ●curtail weed establishment.Incorporate erosion control blankets and/or ●appropriate mulch to reduce erosion and improve soil moisture conditi ons for new planti ngs.Use wetland species in appropriate areas and pond ●bott oms likely to be too wet for regular mowing and maintenance.

NOT THIS

Naturalized rip-rap or cobble stones parti ally buried, broken edges, streambed appearance

THIS

Exposed pipe, no landscape context, exposed rip-rap of uniform color and size, straight edges and square corners


IRRIGATION

Since storm drainage and detenti on areas account for the most signifi cant porti ons of open landscaped space in most projects, their design can greatly impact the amount of irrigati on water demand for a project. Irrigati on and landscape design should correspond to the types of uses planned for the detenti on areas. Areas planned for high pedestrian use such as recreati onal fi elds will require higher irrigati on needs to provide regular, controlled irrigati on levels. More natural areas may be able to minimize or eliminate completely the need for supplemental irrigati on. Landscape designs are encouraged to respond to each site’s unique soil conditi ons and planned hydrology to minimize or eliminate the need for supplemental irrigati on.



MAINTENANCE

Weed ControlThe primary method of weed control during the initi al

establishment period (two to three growing seasons) for seeded areas is regular mowing. Regular mowing helps prevent weed seeds from being produced. Careful spot spraying is also acceptable, but many herbicides aff ect seedling grasses and non-target plants. Always read and follow label directi ons. Aft er the initi al establishment period, if chemical weed controls are needed in the pond bott oms of wet detenti on areas, herbicides should be selected that have an aquati c label. Even herbicides approved for aquati c use should only be used during periods of dry weather and dryer conditi ons to reduce the amount of herbicide that gets into the water itself. Side slopes generally above the high water line can be sprayed with non-aquati c but non-persistent herbicides as per the manufacturer’s recommendati ons.

Catt ails will generally establish in created detenti on areas through natural dispersal. Although they are a nati ve species, they are oft en so competi ti ve that they become a mono-culture if not managed. Catt ails should be suppressed for the fi rst three to fi ve growing seasons to allow less aggressive nati ve species to establish.

Erosion ControlAreas of erosion should be monitored and corrected

to prevent damage to the landscape and storm drainage structures.

Irrigation and FertilizationSupplemental irrigati on will be needed during the

initi al establishment period. However, once established, naturalized drainage and detenti on areas using nati ve plants and species appropriate for the specifi c moisture regimes should not require ferti lizers or supplemental irrigati on aft er establishment. Irrigati on used during establishment can either be reduced or eliminated altogether. Limit the use of ferti lizers in nati ve plant areas.

In detenti on basins that also serve as recreati on fi elds or acti ve neighborhood spaces, permanent irrigati on and more standard ferti lizati on, aerati on, and weed control practi ces are appropriate to keep a more manicured appearance.

MAINTENANCERequired Design Standards:

In all cases the following standards apply:Use regular mowing as a primary weed control ●method during initi al establishment period.Limit use of chemical herbicides, and only use those ●appropriate for conditi ons. Use non persistent herbicides in upland areas, and aquati c approved herbicides near wet, wetland or water areas.Suppress catt ails for the fi rst three to fi ve growing ●seasons to allow less aggressive nati ve species to establish.Monitor and correct areas of erosion. ●Limit irrigati on and ferti lizati on to that needed for ●plant establishment and specifi c designed needs. Naturalized areas with nati ve plants are adapted to Colorado soils so should only require irrigati on during the initi al establishment period, and should not require ferti lizati on. High-use or acti ve recreati on areas will require more regular irrigati on and standard ferti lizati on practi ces.

APPENDICIES: 14

APPENDICES

GLOSSARY OF TERMS & CONCEPTSBase Flow – The porti on of stream fl ow that is not runoff and results from seepage of water from the ground into a channel over ti me. The primary source of running water in a stream during dry weather.

Best Management Practi ce (BMP), nonstructural– Strategies implemented to control stormwater runoff that focus on polluti on preventi on, such as alternati ve site design, educati on, and good housekeeping measures.

Best Management Practi ce (BMP), structural – Engineered devices implemented to control, treat, or prevent stormwater runoff .

Bio-fi ltrati on – The use of vegetati on such as grasses and wetland plants to fi lter and treat stormwater runoff as it is conveyed through an open channel or swale, or collects in an infi ltrati on basin (see Bio-retenti on).

Biological Diversity – The concept of multi ple species or organisms living together in balance with their environment and each other.

Bio-retenti on – The use of vegetati on in retenti on areas designed to allow infi ltrati on of runoff into the ground. The plants provide additi onal pollutant removal and fi ltering functi ons.

Detenti on - The storage and slow release of stormwater following a precipitati on event by means of an excavated pond, enclosed depression, or tank. Detenti on is used for both pollutant removal, stormwater storage, and peak fl ow reducti on. Both wet and dry detenti on methods can be applied.

Evapotranspirati on - The loss of water to the atmosphere through the combined processes of evaporati on and transpirati on, the process by which plants release water they have absorbed into the atmosphere.

Filter Strip - Grassed strips situated along roads or parking areas that remove pollutants from runoff as it passes through, allowing some infi ltrati on, and reducti ons of velocity.

Floodplain - Can be either a natural feature or stati sti cally derived area adjacent to a stream or river where water from the stream or river overfl ows its banks at some frequency during extreme storm events.

Green Roof - A contained space over a building that is covered, parti ally or enti rely, with living plants.

Groundwater - Water that fl ows below the ground surface through saturated soil, glacial deposits, or rock.

Hydrologic Soil Groups - Soil groups based on esti mates of runoff potenti al. Soils are assigned to one of four groups according to the rate of water infi ltrati on when the soils are not protected by vegetati on, are thoroughly wet, and receive precipitati on from long-durati on storms.

Group A• . Soils having a high infi ltrati on rate (low runoff potenti al) when thoroughly wet. These consist mainly of deep, well drained to excessively drained sands or gravelly sands. These soils have a high rate of water transmission.Group B• . Soils having a moderate infi ltrati on rate when thoroughly wet. These consist chiefl y of moderately deep or deep, moderately well drained or well drained soils that have moderately fi ne texture to moderately coarse texture. These soils have a moderate rate of water transmission.Group C• . Soils having a slow infi ltrati on rate when thoroughly wet. These consist chiefl y of soils having a layer that impedes the downward movement of water or soils of moderately fi ne texture or fi ne texture. These soils have a slow rate of water transmission.Group D• . Soils having a very slow infi ltrati on rate (high runoff potenti al) when thoroughly wet. These consist chiefl y of clays that have a high shrink-swell potenti al, soils that have a high water table, soils that have a claypan or clay layer at or near the surface, and soils that are shallow over nearly impervious material. These soils have a very slow rate of water transmission.If a soil is assigned to a dual hydrologic group (A/D, B/D, • or C/D), the fi rst lett er is for drained areas and the second is for undrained areas. Only the soils that in their natural conditi on are in group D are assigned to dual classes.

Hydrology - The science addressing the properti es, distributi on, and circulati on of water across the landscape, through the ground, and in the atmosphere.

Impervious surface - A surface that cannot be penetrated by water such as pavement, rock, or a rooft op and thereby prevents infi ltrati on and generates runoff .

Imperviousness - The percentage of impervious cover within a defi ned area.

APPENDICIES: 15


Infi ltrati on - The process or rate at which water percolates from the land surface into the ground. Infi ltrati on is also a general category of BMP designed to collect runoff and allow it to fl ow through the ground for treatment.

Metered Detenti on and Discharge - A system where stormwater is collected in a cistern pond and then slowly released into the landscape beds or the storm drain in the following hours at the rate that allows for bett er fi ltrati on and is less taxing to the overall community storm drain.

Nati onal Pollutant Discharge Eliminati on System (NPDES) - A provision of the Clean Water Act that prohibits discharge of pollutants into waters of the United States unless a special permit is issued by the EPA, a state, or (where delegated) a tribal government or and Indian reservati on.

Outf all - The point of discharge from a river, pipe, drain, etc. to a receiving body of water.

Peak discharge - The greatest volume of stream fl ow occurring during a storm event.

Pervious - Admitti ng of passage or entrance. Material that permits elements such as water and oxygen to enter and or pass through.

Polluted runoff - Rainwater or snow melt that picks up pollutants and sediments as it runs off roads, highways, parking lots, lawns, agricultural lands, logging areas, mining sites, septi c systems, and other land-use acti viti es that can generate pollutants.

Porous pavement and pavers - Alternati ves to conventi onal asphalt that uti lize a variety of porous media, oft en supported by a structural matrix, concrete grid, or modular pavement, which allow water to percolate though to a sub-base for gradual infi ltrati on.

Retrofi t - The creati on or modifi cati on of a stormwater management practi ce, usually in a developed area, that improves or combines treatment with existi ng stormwater infrastructure.

Runoff - Water from rainfall, snow melt, or otherwise discharged that fl ows across the ground surface instead of infi ltrati ng the ground.

Sanitary sewer system - Underground pipes that carry only domesti c or industrial wastewater to a sewage treatment plant or receiving water.

Sedimentati on - A solid-liquid separati on process uti lizing

gravitati onal sett ling to remove soil or rock parti cles from the water column.

Siltati on - A solid-liquid separati on process uti lizing gravitati onal sett ling to remove fi ne-grained soil or rock parti cles from the water column.

Storm sewer system - A system of pipes and channels that carry stormwater runoff from the surfaces of building, paved surfaces, and the land to discharge areas.

Stormwater - Water derived from a storm event or conveyed through a storm sewer system.

Surface water - Water that fl ows across the land surface, in channels, or is contained in depressions on the land surface (e.g. Runoff , Ponds, Lakes, Rivers, and Streams).

Swale - A natural or human-made open depression or wide, shallow ditch that intermitt ently contains or conveys runoff . Swales can be equipped with an underdrain or other man-made drainage device. and can be used as a BMP to detain and fi lter runoff .

Urban runoff - Runoff derived from urban or suburban land-uses that is disti nguished from agricultural or industrial runoff sources.

Water (hydrologic) cycle - The fl ow and distributi on of water from the sky, to the Earth’s surface, through various routes on or in the Earth, and back to the atmosphere. The main components are precipitati on, infi ltrati on, surface runoff , evapotranspirati on, channel and depression storage, and groundwater.

Water table – The level underground below which the ground is wholly saturated with water.

Watershed - The land area, or catchment, that contributes water to a specifi c water body. All the rain or snow that falls within this area fl ows to the water bodies as surface runoff , in tributary streams, or as groundwater.


natural state and not manicured.Encourage bioswales, etc. in and around site. ●Incenti ve to allow water to be treated at source in rain ●gardens / bioswales / etc.Provide support that will lead to decrease in required ●pond volumes such as narrower streets, pervious pavements, etc. Currently engineering will not allow pervious pavement or bioswalesNo pan requirements in ponds ●Don’t just default to Urban Drainage; allow variati on ●suitable to project type and size. Allow credit for developments that try several LID practi ces even if it can’t be modeled or formulated in U.D. Let’s see if it works provided downstream not aff ected.How can we quanti fy infi ltrati on / to allow for smaller ●ponds?What plants can work in fl at-bott om swales (no ●concrete pan)City inspectors requiring concrete pans! ●Keep in mind expansive clay soils, cannot hold / direct ●water across them without issues.Diff erent standards (maintenance / design /aestheti cs) ●for diff erent uses / districts = industrial vs. retailCivil Engineers tend to “engineer” a soluti on in the ●least amount of spaceIntegrated Design ●Go from uti litarian to “aestheti c” ●Multi use spaces included in fi nal design ●Need more cooperati on between city departments to ●reduce maintenance requirements (onerous) on HOA’sGo for the more natural look. ●Materials: ●

No rock?A. No concrete?B. No verti cal edges?C. No irrigati on? – (nati ve and adapti ve)D.

Green (grass) vs. Green (money) vs. Green ●(sustainable)Flexible aestheti cs per property / project ●Distributed smaller detenti on ●No regional pond. ●Savings from less storm sewer. ●Raised landscape islands converted to depressed ●landscape islandsIncenti ves for: ●

STAKEHOLDER & OPEN HOUSE COMMENTSA landscape plan for all stormwater faciliti es must ●be prepared by a professionally licensed Landscape Architect with experience in stormwater facility design.List possible techniques/soluti ons with examples ●and case studies to help appease those entering into uncharted territory (both applicants and reviewers)…this will help avoid the “pioneers get the arrows, and the sett lers get the land” dilemma.Along with various opti ons, include the design ●criteria to which City Staff will review against. If every applicant and design team needs to justi fy the proposed soluti ons on their own, and spend extra ti me and money getti ng Staff on board, it will serve as a deterrent to implementi ng some of these new techniques. Obviously, the guidelines cannot account for every potenti al opti on, and they need to remain fl uid to allow future soluti ons and innovati ons not yet known. However, to get the ball rolling and encourage more imminent alternati ves, not asking each project to ‘fi ght the batt le’ so-to-speak would be a great benefi t.Please put these boards on the website. ●More Wet Ponds, or fl at bott om, because it provides ●additi onal volumeHow do you handle clay soils? ●Use appropriate landscaping materials ●If using sub drain, provide outlet ●Ponds should have concrete weir – because it provides ●a reference elevati onSlow H2O down to increase infi ltrati on. ●Remove concrete pans to assist / allow areas to be ●more natural. Use planti ng in this area to build upon drainage path.Reevaluate stormwater requirements to over store ●H2O.Take into account H2O uptake of plant material. ●Use of injecti on / percolati on wells to speed ●absorpti on.Combine system with pervious pavement soluti ons to ●maximize usable land.Provide incenti ves for innovati on. ●How can green roofs help with the reducti on / delay of ●stormwater discharge?Incenti ve to developer to allow pond areas to be in ●



Dispersed systemA. Water qualityB.

Slow down the water! ●Regional / Neighborhood detenti on faciliti es vs. each ●site – with fee similar to street over sizing

Regional (City)A. NeighborhoodB. PrivateC.

Infi ll projects ●Smaller faciliti esA. Swales with infi ltrati onB.

Linear detenti on keep larger ponds sizes down ●Inverted landscape islands in parking lots ●Alternati ves for wetland miti gati on similar to Corp of ●Engineers in lieu of fee?May not apply to detenti on ponds ●LID – encourage small ponds close to source ●Concentrati on of surface area ●

Less curb and gutt erA. More infi ltrati onB. *Increased surface areaC. Greenbelts conveying and slowing water D. (check dams) to increase infi ltrati on

Nati ve soils = litt le infi ltrati on but slowing rate through ●bioswales sti ll help with down stream fl owsTucson = standards top in nati on as model ●City needs to be able to accept new ideas ●

Rocky mountain innovati onA. Infi ltrati on? City requires 2X capacity if case it B. doesn’t workInclude innovati on process in standardsC.

Collaborati on – encourage collaborati on among project ●team members and between team and cityCity to take a leadership role in new techniques ●Help developer to understand benefi ts. *Examples of ●successful projects?Example projects schemati cs, concepts illustrated ●Eliminate risk by having guidelines on the books ●Access for maintenance ●Mowing (private Maintenance) ●Backhoes / Dumptrucks for sediment removal (city) ●Partnership between private and city ●Gently sloping sod, few trees ●No walls? ●Limit walls to allow maintenance ●Underground detenti on? ●How do you deal with long term maintenance? ●

Standards vs. Guidelines ●Prescripti ve vs. Proscripti ve ●Requirement for Landscape Architect on design team ●Combinati on? If walls then upgrade ●Engineering staff on team ●LUCASS staff on team ●Life cycle vs. Front end cost ●Conti nue to promote growth and development ●Multi ple use = multi ple approaches ●Diffi cult with litt le used areas ●No ferti lizer unless play fi elds ●No irrigati on (except during establishment) ●Required ground cover ●Context for plant types ●

Categories for use, wetland, soil type, landscape, A. maintenanceReview Urban Drainage StandardsB. New development vs. Infi ll / redevelopmentC.

Documents

11-05-09 FC Stormwater Standards and Guidelines · 2018-11-28 · Angela Milewski - BHA Design Inc. Jason Messaros - BHA Design Inc. Glen Schlueter - City of Fort Collins Uti liti